PROJECT SUMMARY Pre-exposure prophylaxis (PrEP) with emtricitibine/tenofovir disoproxyl fumarate (FTC/TDF) has been shown to dramatically reduce transmission of HIV in men who have sex with men (MSM). However, as an antiretroviral medication, it does not protect against other sexually transmitted infections (STIs). Currently in the US, STI rates are at an ?unprecedented high,? according to the Centers for Disease Control and Prevention. These elevated rates are especially pronounced in MSM prescribed PrEP and represent a crucial public health problem that requires immediate attention. Dr. Clement's K23 proposal will focus on addressing this problem through the use of mobile health (mHealth) technology in a critically important population with profound health disparities, Black MSM in the South. First, to understand predictors of STIs, she will explore the relationship between social factors (e.g. peer support and risk behaviors) and STI incidence. These relationships will inform broader research efforts, and specifically for the purpose of this application, allow the proposed intervention to focus on those at highest risk for STIs. Second, she will investigate facilitators and barriers to STI risk reduction practices through in-depth interviews (IDIs) with Black MSM PrEP users. Operating under the framework that social isolation and lack of peer support drive sexual risk taking in Black MSM, she will specifically inquire about peer support as a facilitator to STI risk reduction practices, and gather initial feedback on the peer support features of the mSMART application (?app?). Data will be used to adapt the app, which will be further assessed in focus groups. These qualitative studies will give valuable insight into factors driving sexual risk taking that the mHealth app will then target. Third, in a pilot investigation of Black MSM PrEP users with poorly predictive STI risk factors, as identified in the first aim, she will conduct a randomized study to determine the feasibility and preliminary impact of the adapted mSMART app in reducing STI incidence. Through this proposal, Dr. Clement will build upon her experience in STIs with continued pursuit of critical public health research, and as a result be prepared to become a national leader in the field of HIV/STI prevention. Didactic coursework will bolster Dr. Clement's quantitative analytic skills and solidify her knowledge base, while formal and informal instruction in qualitative science will help her establish a new skillset that will serve fruitful in future investigations. Additionally, she will gain training and experience in mHealth technology, a growing field with broad applications for health care access and delivery. The mentorship team, led by Dr. Susanna Naggie, an experienced HIV investigator, will include experts in behavioral science related to PrEP and qualitative research (Dr. Amy Corneli), mHealth technology (Dr. Nirmish Shah), and biostatistics (Dr. Shein-Chung Chow). Also included as collaborators are Dr. Arlene Sea, an expert in STIs who is Medical Director of the Durham County Department of Public Health, Dr. Mehri McKellar, the Medical Director of the Duke PrEP clinic, Dr. John Mitchell, a clinical psychologist who has pioneered the mobile app mSMART in PrEP users, and Dr. Sara LeGrand, a health services researcher with extensive experience developing and testing mHealth interventions for minority MSM populations. The proposed aims and accompanying training plan will allow Dr. Clement to mature into an independent researcher in HIV/STI prevention and provide a basis for an R01 to implement her mobile technology intervention for STI prevention in Black MSM PrEP users.